• Tribology and Lubricants
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• v.37 no.6
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• pp.253-260
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• 2021

Metal pipes are used in a wide range of applications, from plumbing systems of large construction sites to small devices such as medical tools. When a liquid is enforced to flow through a metal pipe, a higher flow rate is beneficial for higher efficiency. Using high pressures can enhance the flow rate yet can be harmful for medical applications. Thus, we consider an optimal geometrical design to increase the flow rate in medical devices. In this study, we focus on cannulas, which are widely used small metal pipes for surgical procedures, such as liposuction. We characterize the internal flow rate driven by a negative pressure and explore its dependence on the key design parameters. We quantitatively analyze the suction characteristics for each design variable by conducting computational fluid dynamics simulations. In addition, we build a suction performance measurement system which enables the translational motion of cannulas with pre-programmed velocity for experimental validation. The inner diameter, section geometry, and hole configuration are the design factors to be evaluated. The effect of the inner diameter dominates over that of section geometry and hole configuration. In addition, the circular tube shape provides the maximum flow rate among the elliptical geometries. Once the flow rate exceeds a critical value, the rate becomes independent of the number and width of the suction holes. Finally, we introduce a slippery liquid-infused nanoporous surface (SLIPS) coating using nanoparticles and hydrophobic lubricants that effectively improves the flow rate and antifouling property of cannulas without altering the geometrical design parameter.

• Journal of ILASS-Korea
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• v.28 no.1
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• pp.1-9
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• 2023

In the cylinder of gasoline direct injection engines, the spray targeting from injectors is of great significance for fuel consumption and pollutant emissions. The automotive industry is putting a lot of effort into improving injector targeting accuracy. To improve the targeting accuracy of injectors, it is necessary to develop models that can predict the spray targeting positions. When developing spray targeting models, the most used technique is computational fluid dynamics (CFD). Recently, due to the superiority of machine learning in prediction accuracy, the application of machine learning in this field is also receiving constant attention. The purpose of this study is to build a machine learning model that can accurately predict spray targeting based on the design parameters of injectors. To achieve this goal, this study firstly used laser sheet beam visualization equipment to obtain many spray cross-sectional images of injectors with different parameters at different injection pressures and measurement planes. The spray images were processed by MATLAB code to get the targeting coordinates of sprays. A total of four models were used for the prediction of spray targeting coordinates, namely ANN, LSTM, Conv1D and Conv1D & LSTM. Features fed into the machine learning model include injector design parameters, injection conditions, and measurement planes. Labels to be output from the model are spray targeting coordinates. In addition, the spray data of 7 injectors were used for model training, and the spray data of the remaining one injector were used for model performance verification. Finally, the prediction performance of the model was evaluated by R² and RMSE. It is found that the Conv1D&LSTM model has the highest accuracy in predicting the spray targeting coordinates, which can reach 98%. In addition, the prediction bias of the model becomes larger as the distance from the injector tip increases.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1B
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• pp.7-14
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• 2006

The radar relationship was estimated for the selected rainfall event at Yeongchun station within Chungjudam basin where the discharge record was the range of from 1,000 CMS to 9,000 CMS. By calibrating the rainfall coefficient parameter estimated by radar relationship in small hydrology basin, rainfall with the topography properties was calculated. Three different rainfall estimation methods were compared:(1) radar relationship method (2) Thiessen method (3) Isohyetal method (4) Inverse distance method. Basin model was built by applying HEC-GeoHMS which uses digital elevation model to extract hydrological characteristic and generate river network. The proposed basin model was used as an input to HEC-HMS to build a runoff model. The runoff estimation model applying radar data showed the good result. It is proposed that the radar data would produce more rapid and accurate runoff forecasting especially in the case of the partially concentrated rainfall due to the atmospheric change. The proposed radar relationship could efficiently estimate the rainfall on the study area(Chungjudam basin).

• Structural Engineering and Mechanics
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• v.90 no.1
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• pp.27-40
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• 2024

The prediction of VIV amplitude is essential for the design and fatigue life estimation of steel tubes in tubular transmission towers. Limited to costly and time-consuming traditional experimental and computational fluid dynamics (CFD) methods, a machine learning (ML)-based method is proposed to efficiently predict the VIV amplitude of steel tubes in transmission towers. Firstly, by introducing the first-order mode shape to the two-dimensional CFD method, a simplified response analysis method (SRAM) is presented to calculate the VIV amplitude of steel tubes in transmission towers, which enables to build a dataset for training ML models. Then, by taking mass ratio M^*, damping ratio ξ, and reduced velocity U^* as the input variables, a Kriging-based prediction method (KPM) is further proposed to estimate the VIV amplitude of steel tubes in transmission towers by combining the SRAM with the Kriging-based ML model. Finally, the feasibility and effectiveness of the proposed methods are demonstrated by using three full-scale steel tubes with C-shaped, Cross-shaped, and Flange-plate joints, respectively. The results show that the SRAM can reasonably calculate the VIV amplitude, in which the relative errors of VIV maximum amplitude in three examples are less than 6%. Meanwhile, the KPM can well predict the VIV amplitude of steel tubes in transmission towers within the studied range of M^*, ξ and U^*. Particularly, the KPM presents an excellent capability in estimating the VIV maximum amplitude by using the reduced damping parameter S_G.

• Journal of Distribution Research
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• v.15 no.1
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• pp.25-47
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• 2010

CS is one of the major concerns of managers in the world because it is well known to be a key medium construct for firms' superior outcome. One of the major agents for CS management is retailers. Firms try to manage not only employees but also retailers to promote CS behaviors. And so diverse incentives are used to promote their CS behaviors under diverse channel setting such as multi-channel. However in spite of the rising needs there has been scarce studies on the optimal incentive structure for a manufacturer to offer competing retailers at the multi-channel. In this paper, we try to find better way for a manufacturer to promote the competing retailers' CS behaviors. We investigated how to promote the retailers' CS behavior via game-theoretic modeling. Especially, we focus on the possible incentive, CS bonus type reward introduced in the studies of Hauser, Simester, and Wernerfelt(1994) and Chu and Desai(1995). We build up a multi stage complete information game and derive a subgame perfect equilibrium using backward induction. Stages of the game are as following. (Stage 1) Manufacturer sets wholesale price(w) and CS bonus($\eta$). (Stage 2) Both retailers in competition set CS effort level($e_i$) and retail price($p_i$) simultaneously. (Stage 3) Consumers make purchasing decisions based on the manufacturer's initial reputation and retailers' CS efforts.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.12
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• pp.1870-1883
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• 1993

In this paper, in order to build up the User Network Interface based on ATM, a study on traffic control techniques which should be performed by main function groups-B 75,5 NT2, LEX-is discussed. The structure of B-NT2 which is the most important function group In the User Network Interface is defined in quite a simple manner in addition, the functional blocks of LEX are defined in a similar manner as those of B NT2. It is possible to distribute total traffic control functions by using the similarities between B-NT2 and LEX and by allocating virtual path identifiers fixedly according to the characteristics of the traffics. For the traffic control techniques of ATM, relations among Connection Admtsslon Control, Usage Parameter Control and Bandwidth Allocation Control are defined and Multi Rule Base structure to realize optimal control functions according to the characteristics of the source traffics is proposed. And the Real-time Variable Window algorithmsimply designed to be suitable for the Multi Rule Base architecture is also proposed. The performances of the proposed algorithm are analyzed through the computer simulation by generating on-off source traffic in a virtual system that has the form of the proposed hardware. The analyzed results show that the distributed control is possible and that the implementation of the proposed architecture and algorithm is possible.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.1
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• pp.103-112
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• 1984

This study is an effort to develop a series of empirical procedure for the determination of design flood for a small watershed based on the unit hydrograph theory. It is shown that a flood discharge of a watershed with a specific return period can be expressed as a product of its watershed area, rainfall factor, runoff factor and flood peak reduction factor. Since the procedures for the determination of rainfall factor and runoff factor were already developed in the previous study (13) a series of step-by-step procedure is devised to empirically determine the flood peak reduction factor in the present study. Using the methodology developed herein the 50-year design flood, which is of concern in the drainage of agricultural lands, is estimated for a watershed on upper Kyungan River and compared with the design floods by the existing methods now in use. The flood peak reduction factor was correlated with the dimensionless parameter consisted of the rainfall duration divided by the basin lag time, which was computed from the derived unit hydrographs by the method of moment. The unit hydrographs of various durations were synthesized by the method of build up and S-curve. A multiple correlation was also made between the basin lag time and the physiographic parameters of the watershed, i.e., the stream length and the average stream slope.

• Journal of muscle and joint health
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• v.6 no.1
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• pp.100-135
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• 1999

Typical symptoms of rheumatic disease affect overall daily living and cause severe stress. Individuals afflicted with rheumatic disease have many illness-related stresses. Pain was the predominantly perceived stress followed by limitation in mobility, difficulties in carrying out activities of daily living. helplessness, dependency on others, threat to self-esteem, interference in social activity, interference in family relationships. difficulties performing at work, and discomfort of the treatment. Patients with chronic arthritis are subjected to long periods of continuous stress, which may require the management by the health care provider. In these cases, the purpose of the nursing is helping to promote health through supporting patient's coping. Therefore, for the nursing intervention to be effective, it is critical to build a theoretical framework that describes stress-coping for chronic arthritis. Thus, the purpose of this dissertation is to present a theoretical framework which describes the stress-coping processes and to empirically test pathos of this framework for the people with chronic arthritis. The foundation upon which this framework is built in the Erickson, Tomlin, and Swain(1983) theory of Modeling and role-Modeling. The subjects were 275 patients with rheumatoid arthritis or osteoarthritis who visited the outpatient clinic. A hypothetical model of stress-coping was tested by covariance structure analysis with PC-LISREL 8.12 program. As a result, the overall fit was good(Chi-square=94.49, P=0.00, RMR=0.067, GFI=0.95, AGFI=0.91, NNFI=0.93, NFI=0.91) for the hypothetical model. The results of hypothesis testing were as follows : Basic need satisfaction had a statistically significant influence on illness-related experience, emotional stress and coping resources. Internal health locus of control had a statistically significant influence on coping resources. However, independent variables(basic need satisfaction, internal health locus of control, illness-related experience, emotional stress and coping resource) did not have significantly influence on coping. And then, the hypothetical model was modified by considering both the theoretical implication and statistical significance of the parameter estimates. The revised model had a better fit to the data(Chi-square=83.11(P=0.00), RMR=0.061, GFI=0.96, AGFI=0.92, NNFI=0.95, NFI=0.92). Hypothesis emerged from the revised model was tested. The results of hypothesis testing were as follows : Basic need satisfaction had a statistically significant influence on illness-related experience, emotional stress and coping resources. Internal health locus of control had a statistically significant influence on illness-related experience and coping resources. Internal health locus of control, illness-related experience, emotional stress and coping resources had a significantly influence on coping. According to the results of this dissertation, basic need satisfaction and internal health locus of control play a central role in appraisal of illness-related experience and coping resources. And illness related-experience, emotional stress, and coping resources affect on coping activities. In summary, nursing interventions to enhance basic need satisfaction and internal health locus of control will decrease illness related experience and emotional stress and increase coping resources. Increased coping resources will prompt coping activities.

• Journal of Animal Science and Technology
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• v.62 no.4
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• pp.429-437
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• 2020

This study was conducted to construct basic data for the selection of elite cows by analyzing the estimated breeding value (EBV) and accuracy using the pedigree of Hanwoo cows in Gyeongnam. The phenotype trait used in the analysis are the carcass weight (CWT), eye muscle area (EMA), backfat thickness (BFT) and marbling score (MS). The pedigree of the test group and reference group was collected to build a pedigree structure and a numeric relationship matrix (NRM). The EBV, genetic parameters and accuracy were estimated by applying NRM to the best linear unbiased prediction (BLUP) multiple-trait animal model of the BLUPF90 program. Looking at the pedigree structure of the test group, there were a total of 2,371 cows born between 2003 to 2009, of these 603 cows had basic registration (25%), 562 cows had pedigree registration (24%) and 1,206 cows had advanced registration (51%). The proportion of pedigree registered cows was relatively low but it gradually increased and reached a point of 20,847 cows (68%) between 2010 to 2017. Looking at the change in the EBV, the CWT improved from 4.992 kg to 9.885 kg, the EMA from 0.970 ㎠ to 2.466 ㎠, the BFT from -0.186 mm to -0.357 mm, and the MS from 0.328 to 0.559 points. As a result of genetic parameter estimation, the heritability of CWT, EMA, BFT, and MS were 0.587, 0.416, 0.476, and 0.571, respectively, and the accuracy of those were estimated to be 0.559, 0.551, 0.554, and 0.558, respectively. Selection of superior genetic breed and efficient improvement could be possible if cow ability verification is implemented by using the accurate pedigree of each individual in the farms.

• Korean Journal of Poultry Science
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• v.19 no.3
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• pp.113-123
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• 1992

This study was carried out to build up new synthetic egg Production lines which had sex linked gene for feather color sexing and had also superior combining ability for producing the best commercial chicks. In order to make autosexing layer line, the commercial layers which had Z$^{s}$ Z$^{s}$ and Z$^{s}$ W were mated. Among progeny, the chicks which had homozygote of silver gene and non-silver gene were selected for making dam and sire lines. Afterwards the closed flock breeding method was utilized to improve general performances of the each line. The performances of egg production in synthetic line were 161 day for age at sexual maturity, 219 eggs for total egg number to 60 weeks of age, 84% for hen-day egg production and 619 for average egg weight. There was no difference in egg production between new synthetic lines and imported breeds. In the analysis of genetic trends, the estimates of genetic parameter in the autosexing lines were similar to those of the general population of layer breeders. This results indicated the consistency of genetic variation from this selection.